In its basic form, an electronic camera, such as digital still camera or a camera embedded in a mobile (cell) phone or in a tablet computer includes two components: (1) a lens module comprising a set of one or more plastic or glass lens elements and used to create an optical image of the viewed scene, and (2) an image sensor (e.g., CMOS or CCD), which converts the optical image to the electronic domain, where the image can be processed and stored. There are different types of electronic (or digital) cameras ranging by application (e.g., regular SLR, camera-phone, automotive, security and medical) and by functionality (e.g., with or without auto-focus). The simplest cameras are those in which the lens module is fixed in position with respect to the image sensor. These cameras are often called fixed-focus cameras, where the camera is focused to a pre-determined distance. Objects that fall within the depth of field of the camera can be captured sharply and those which fall beyond the depth of field will be blurred. In more advanced cameras, the position of the lens module (or at least one lens element in the lens module) can be changed by means of an actuator and the focus distance can be changed in accordance with the captured object or scene. In these cameras it is possible to capture objects from a very short distance (e.g., 10 cm) to infinity.
Some advanced camera designs may include different groups of lenses that can move with respect to each other and hence change the effective focal length of the camera, which results in optical zoom capability. The trend in digital still cameras is to increase the zooming capabilities (e.g. to 5×, 10× or more) and, in cellphone cameras, to decrease the pixel size and increase the pixel count. These trends result in greater sensitivity to hand-shake or in a need for longer exposure time. This has created a need for optical image stabilization (OIS), which now appears in advanced cameras. In OIS-enabled cameras, the lens or camera module can change its lateral position or tilt angle in a fast manner to cancel the hand-shake during the image capture.
In compact (miniature) camera modules, the most ubiquitous form of an actuator is the Voice-Coil Motor (VCM), which includes a coil (wire turned on a cylinder), fixed (or “permanent” or “hard”) magnets and springs. When current is driven through the coil, an electro-magnetic (EM) force is applied and the lens module changes position. While the VCM is considered a mature technology, it is costly, large in size, uses rare-earth magnets, is slow in operation and consumes high power. Therefore, there is a need for, and it would be advantageous to have technical advances which overcome the shortcomings of VCM and related technologies.